1. Field of the Invention
The present invention relates generally to forming of honeycomb core and, more specifically, to computer-controlled tooling capable of providing an adjustable three dimensional surface for forming honeycomb core articles with the capability of applying or directing heated air or gas through the honeycomb core cells as well as providing rapid contour changes. The mechanism of the invention is comprised of a plurality of assembled modules which act in concert with one another to effect the work operation.
2. Description of the Prior Art
Many types of honeycomb core are traditionally cold or hot press-formed. Core can be hot-formed on a heated press, or oven-heated and formed on a non-heated press, both traditionally using fixed-contour machined or cast dies to impart the needed three dimensional contours to the exterior surfaces. Honeycomb core is also roll-formed and/or contour machined to achieve the desired external contours. Roll forming is generally limited to honeycomb core which has ruled surfaces and cannot be used effectively to produce formed honeycomb core with contours that change in two orthogonal directions, both normal to the direction of the cells. Three-dimensional contours are the most expensive to produce and the tools are not easily adapted to other shapes. Individual three-dimensional contour dies are costly and time consuming to make, and require time and storage space. A cheaper, faster, more adaptable methodology is needed which can be used for a large variety of honeycomb core shapes. The method and hardware should be easily adapted to existing equipment for widespread industry acceptance.
Since the cost for an adjustable forming die is high relative to the cost for fixed-contour dies, the use of discrete tooling should be considered when very few pieces each of a large variety of core details are needed. The converse is generally also true. Formed honeycomb core is generally used in aerospace applications where each aircraft requires a large variety of honeycomb core shapes. Since the economic viability of replacing a honeycomb core forming system using many fixed-contour dies with an adjustable-die system using a single discrete adjustable-contour die depends upon the number of fixed tools that an adjustable die can replace, aircraft manufacturing is well-suited to the discrete, adjustable-tooling approach. Another cost savings from lower labor requirements to fit generically formed core can be realized. Additionally, the referenced modular design approaches allows the plan form of the discrete, adjustable die to be changed inexpensively, if needed to different length/width combinations by adding or subtracting modules mounted to oversize base plates. The tooling has been described in detail in other disclosures referenced in the Appendix, many of which are specifically designed for stretch forming of sheet metal. Nonobvious modifications to previously-disclosed tooling and forming methods are needed however to adapt the prior-disclosed tooling and methods to acceptably form honeycomb core.
Discrete, self-adjusting form tools have the capability to change shape and form honeycomb core very rapidly using computer control. They can store and retrieve contour information for many three-dimensional shapes in the form of data files stored within computer memory. The concept of "modularity" as introduced by U.S. Pat. No. 5,954,175 entitled "Modularized Parallel Drivetrain" and U.S. Pat. No. 6,012,314 entitled "Individual-Motor Pin Module" is suggested for large, reconfigurable form dies. This approach saves money through the use of repetitive low-cost, high quality castings for geartrain or drive motor housings and bases and eases problems with wiring, assembly, troubleshooting, servicing, maintenance, repair and replacement tasks. Since improper movement of just one pin can cause rejection of a finished piece of honeycomb core, rapid repair with minimum downtime is therefore critical. Discrete dies should have the capability to rapidly replace components and assemblies from acceptable spares stock. The use of modular design construction for large dies helps to minimize downtime. The disclosures of the above-referenced applications are hereby incorporated into this disclosure in their entirety by reference.
Also, since honeycomb core is generally press-formed using fixed, three-dimensionally contoured dies, the springback in the honeycomb core cells is largely dependent upon the die shape and partly dependent upon the changing forming temperature of the core, die, press force and timing application. Fixed dies do not have the ability to change their own contour if an improper amount of springback was designed into the final die shape. Nor do fixed-contour dies have the ability to rapidly, accurately, and consistently adapt to engineering changes involving shape. Expensive machining rework and/or extra labor is needed.
Typical of the prior art are U.S. Pat. No. 5,546,784 to Haas et al. which discloses an adjustable form die, U.S. Pat. No. 2,280,359 to Trudell which discloses a forming apparatus with rubber blocks to conform to the mold, and U.S. Pat. No. 3,081,129 to Ridder which discloses a test chair with an array of plungers with rubber end caps.
It was with knowledge of the foregoing that the present invention has been conceived and is now reduced to practice.